Hello,
i was thinking about the difference between NIS and AD and i would like to ask you this: When you have a windows network and you have active directory, you can have roaming accounts, which means that your data are being saved to the server. Now, i know that this can be done also in Linux, but what i do not know is if in Linux works the same way. I mean that If you have a laptop connected to an AD, you don't have to be always connected to the server in order to get your files. Only a copy of them is saved to the server and a copy to the laptop. CAN this happent also in Linux?

What you're looking for is more of an offline file management, and not really a function of NIS. NIS provides basic authentication. Windows does have options to make files available when offline, but the only thing that I can suggest is to check for file compare tools, or something of the sort. Or even a shell script to compare the dates between the two.